The present invention relates to a recording method and a recording apparatus for a disc-type recording media such as an optical disc and other diverse types of recording media The present invention makes it possible to achieve next information to be written continuously from a recording end of previously recorded information, such that there will be less disturbance in synchronization at a write splicing position between the previous information and the subsequent information during reproduction.
When new information is additionally written, following a recording end of previous information in a successive recording type medium such as a recordable or rewritable optical disc, there may be a discontinuous state where a frequency of the recorded signal and a bit clock for reading of the recorded information do not coincide with each other. Otherwise, there may be a disagreement in phase between frames of the previously recorded information and the newly added information. In such a case, synchronization will be disturbed at the additional writing position with a resultant read error when the recorded information is reproduced after adding the new information. Thus, in the additional writing of new information, it is necessary to continuously write the new information in a continuous state where the recorded information agrees to the frequency of the bit clock, or there is an agreement in the phase of the frames of the recorded information. More preferably, these frequency and phase should be both in agreement between the preceding session and the succeeding session of the recorded information.
Referring to FIG. 2, a conventional method for additionally writing new information to a CD-R/RW disc (to a CD-R disc or a CD-RW disc) will be briefly described. A read signal (EFM signal) of recorded information of the CD-R/RW disc is supplied to a phase-locked loop circuit 10, and the phase thereof is compared, by a phase comparator 12, with that of a signal obtained by dividing an oscillation clock of a VCO (voltage control oscillator) 14 by a frequency divider 16 in a predetermined manner. A predetermined gain is imparted to the phase comparison output by an amplifier 18, and supplied to a control input terminal of the VCO 14 through the intermediary of a loop filter 20 to control the oscillation frequency and phase thereof This causes the VCO 14 to create a read clock synchronized to a bit clock of the read signal. The read signal is reproduced, using the read clock as an operating clock. In parallel to the creation of the read clock, ATIP information that has been recorded beforehand by FM modulation in the form of a pre-recorded signal in a wobble of a pre-groove is demodulated. A synchronization signal included in the demodulated ATIP information (if a synchronization signal is missing, then an interpolation signal produced by counting one cycle of the succeeding synchronization signal from the preceding synchronization signal) is supplied to a phase-locked loop circuit 22, and the phase thereof is compared, by a phase comparator 24, with the phase of the signal obtained by dividing an oscillation clock of a VCO 26 in a predetermined manner by a frequency divider 28. A predetermined gain is imparted to the phase comparison output by an amplifier 30, and supplied to a control input terminal of the VCO 26 through the intermediary of a loop filter 32 to control the oscillation frequency and phase thereof. This causes the VCO 26 to create a write clock synchronized to the synchronization signal of the ATIP information.
To perform additional writing, reading is started from a position before the recording end of recorded information, and the read signal is reproduced using the read clock. At a timing when the read position reaches the recording end of the previous information, a write signal is generated in synchronization with the write clock, and a laser beam of an optical pickup is modulated by the write signal to start writing. In this manner, the additional writing is performed. Spindle control is carried out on the basis of the read clock or the pre-recorded signal before the additional writing position is reached, then carried out on the basis of the pre-recorded signal after the additional writing position is reached. The spindle motor is phase-locked loop controlled so that these signals are obtained at predetermined frequencies.
Another conventional method for additionally writing new information to a CD-R/RW disc will be described with reference to FIG. 3. A read signal (EFM signal) of the recorded information of a CD-R/RW disc 34 is supplied to a phase-locked loop circuit 36, and the phase thereof is compared, by a phase comparator 38 with that of a signal obtained by dividing an oscillation clock of a VCO 40 by a frequency divider 42 in a predetermined manner. A predetermined gain is imparted to the phase comparison output by an amplifier 44, and supplied to a control input terminal of the VCO 40 through the intermediary of a loop filter 46 to control the oscillation frequency and phase of the VCO 40. This causes the VCO 40 to generate a read clock synchronized to a bit clock of the read signal. The read signal is reproduced, using the read clock as an operating clock.
A reference clock is issued from a clock oscillator 48. The reference clock is divided by a frequency divider 50 in a predetermined manner to create a signal having a frequency that corresponds to a wobble signal. A phase comparator 52 compares the phase of the divided reference clock with the phase of the wobble signal detected from the CD-R/RW disc 34. The phase comparison output controls a drive of a spindle motor 56 through the intermediary of a loop filter 54. Thus, the spindle motor 56 is controlled so that the wobble signal detected from the CD-R/RW disc 34 has a predetermined frequency. The reference clock issued from the clock oscillator 48 is divided in a predetermined manner by a frequency divider 58 to create a write clock.
To perform additional writing, reading is begun at a position before the recording end of the previous information while carrying out the spindle motor control based on the wobble signal, and the read signal is reproduced using the read clock. At a timing when the read position reaches the recording end of the previous information, a write signal is generated in synchronization with the write clock, and a laser beam of an optical pickup is modulated by the write signal to start writing. In this manner, the additional writing is performed.
According to the additional writing method based on the configuration shown in FIG. 2, the timing of the synchronization signal included in the ATIP information and the timing of a sub code frame synchronization signal of a read EFM signal of the recorded information do not necessarily coincide with each other (an error of −2 to +2 EFM frame is allowed according to Orange Book Standard). Therefore, new information to be recorded in synchronization with the synchronization signal included in the ATIP information is recorded with a deviation equivalent to the error from the recorded information preceding the additional writing position. When the disc that contains the additional writing is reproduced, the synchronization will be disturbed at the additional writing position, leading to a read error during the reproduction from time to time.
According to the additional writing method based on the configuration shown in FIG. 3, even when the reference clock is used to control the spindle motor 56, the revolution thereof develops a wow flutter, and wow flutter components are superposed on the read signal. For this reason, the read clock generated from the read signal and the write clock generated from the reference clock will have a deviation due to the wow flutter frequency and phase. Hence, when the disc in which additional writing has been performed is played back, the synchronization is disturbed at the additional writing position, resulting in a read error during playback from time to time.
There is still another conventional method for additional writing disclosed in Japanese Unexamined Patent Publication No. 2000-40302. However, the oscillation frequency of a VCO varies when additional writing is begun, causing synchronization to be disturbed at an additional writing position, leading to a possibility of the occurrence of a read error during reproduction.